Gas-lift control



' Patented Aug. 10, 1943 GAS -IJF1 CONTROL Hendrik Pieter de Wit,Casigua, Venezuela, as-

signor to Shell Development Company, San Francisco, Calif., acorporation 01' Delaware Application August 5, 1941, Serial No. 405,563

8 Claims. (01. 103-240) This invention relates to an automatic timingdevice for controlling the flow of oil from a well and pertains moreparticularly to a device for automatically controlling the intermittentsupply of compressed gas to gas-lift pumps.

In most gas-lift devices the duration of the working period, that is, ofthe time during which gas is supplied to the gas-lift pump, isindependent of fluctuations in the pressure of the gas supply and ofvariations in the quantity of well liquid being raised. Thus, theworking period is generally longer than necessary, and the gasconswnption is higher than the optimum.

Also, in many gas-lift systems, central gas distributors have been used,which cause the valves controlling the flow of pressure gas toindividual wells to open and close in succession, so that the workingperiods do not coincide, thereby avoiding overlapping working periodswhich may cause violent pressure fluctuations throughout the system.However, such central control devices are not easily subject to finecontrol so asto obtain the optimum gas consumption. The working periodsfor the various wells are generally longer than necessary, andconsequently there is some waste of gas.

It is therefore an object of this invention to provide a gas-lift systemhaving a central gas supply intermitter or regulator capable of seriallyspacing the working periods of individual wells, and means associatedwith each well and responsive to the liquid discharged therefrom forterminating the working period of said well independently of the centralintermitter, whereby an economical consumption of pressure gas isinsured.

It is another object to provide an intermittent gas-lift system havingautomatic means for controlling the supply of pressure gas to each well,whereby the need for fine manual adjustment of the working periods ofthe individual wells is eliminated.

It is another object to provide a gas-lift system attaining the aboveobjects, which system is mechanically simple and advantageously flexiblefor application to varying field conditions.

Briefly, these and other objects are attained by the present gas-liftcontrol system wherein a central timing device serially spaces theclosure or completion of electrical circuits energizingelectrically-actuated valves which control the supply of pressure gas tothe individual wells, and interrupter means associated with each welladapted to break the electrical circuit and thereby to stop the input ofpressure gas for said well in response to flow of oil therefrom.

header The present invention will be more clearly un derstood from thefollowing description oil a preferred embodiment taken with reference tothe drawings, wherein:

Figure I is a diagrammatic view of the present,

ferred embodiment of the interrupter switch mechanism.

The gas-lift control system of the present invention is described inrelation to a pump having a displacement chamber and an eduction tube,although the present device may b applied equally well to otherintermittent gas-lift pumps. Referring to well A shown in verticalsection in Figure 1, a casing 2 having a perforated liner 3 attached tothe lower end thereofis placed in a borehole l. Depending within thecasing 2 is a tubing string 4 having at the bottom thereof an enlargedportion forming a displacement chamber 5. An inwardly-opening checkvalve 6 is provided in the lower portion of chamber 5 to permit wellliquid to accumulate therein. Extending downwards through the tubingstring 4 and into the displacement chamber is an eduction tube 1. Inoperation, liquid from the producing formations surrounding the boreholeis allowed to flow through the perforations oi the liner 3 into thechamber 5 through the check valve 6 when the pressure in chamber 5 issufllciently reduced: the accumulated liquid is then lifted through theeduction tube 7 by compressed gas supplied from a gas supply pipe Hi tothe annular space 9 between the tubing string 4 and eduction tube 1; thecheck valve 6 in the lower portion 01' the chamber 5 closes to avoidapplying high pressures to the producingformations, which may causeproduction losses; the well liquid and the gas raising said liquid aredischarged from the eduction tube 1 through discharge or oil flow lineto attached thereto at the well head.

To effect this operation of the elements described or their equivalentswhich, in combination, may be referred to as a gas-lift pump, thepressure gas or working fluid in the pipe or line It, which communicateswith the gas supply I5, is alternately admitted into the annular space 9and shut oi! therefrom by means of an electrically-operated controlvalve 24. In the general arrangement of the present gas-lift controlsystem. as shown in Figure I, the operation of the control valve 24 foreach well is controlled by the combination comprising anelectricallyoperated central timing device or regulator 2|, which alsogoverns the operation of the control valves 24 in a plurality of wells.8. C, D, etc.. an electrical current source 22 and, for each well, acurrent interrupter 21 actuated by or responsive to the liquid flow ordischarge in line II and adapted to break the electrical currentactuating the control valve 24 in response to a flow or oil from thedischarge line l9.

Referring to Figures II and DI showing the various parts in more detail,a preferred embodiment of the central intermitter or regulator 2icomprises a housing 30, an electric motor 3| connected to the electricalsource 22 which may comprise a cell, storage battery, or the terminalsof any suitable power supply system, and clockwork or escapement means32 or the like adapted to regulate the rotation of the motor shaft 33.Attached to the shaft 33 and rotatable therewith is a disk 34, or othersuitable means, provided with an insulated ring 35 in its outercircumferential portion. An electrical contact 35 attached to theinsulated ring 35 is carried in a circular path by the rotation of thedisk 34 and makes contact with a stationary ring 40 having suitablyspaced sector contacts 4| between insulating sectors 4la, as shown moreclearly in Figure I11. To each contact 41 is connected an electricalconduit 42 leading to a gas-injection control valve 24. By means of astationary contact 43 attached to the wall of the housing 30 and heldagainst .the rotating ring 35, electrical current may pass from theelectrical current source 22 through the stationary contact 43, therotating ring 35, the rotating contact 36, and one of the insulatedcontacts 4| in the stationary ring 40 through the electrical conductors42 comprising contacts 90-9i to an electrically-operated valve 24.Suitable connections may also be provided between the electrical currentsource 22 and each control valve 24 through the ground. For example,when the distance from the central regulator 2| to the valve 24 isgreater than about 400 feet, the conductor 45 may be eliminated bygrounding the lower terminal of the source 22 and the left-hand terminalof valve 24. If desired, the upper end of the motor shaft 33 may beterminated outside the housing 30 and fitted with a pointer 31 toindicate which well is bein produced at the moment by the position ofthe pointer in relation to a dial r markings (not shown) formed on theadjacent upper surface of the housing. Instead, signal lights (notshown) may be provided in series with the various cir-.

cuits to the wells for the same purpose. It is to be noted that thelength of the contact sectors 4| may be varied to roughly set the lengthof the gas admission periods for the different wells and that, further,the various contacts 4i may be combined, if desired, into groups orcombinations for timing the gas injection periods to suit individualwell requirements.

The gas control valve 24 may be any suitable electro-magnetic valve orthe like. For example, in a preferred mechanism a solenoid-operatedpilot valve 48 controls a diaphragm-motor valve 49 which, in turn,controls the passage of gas supply through the gas injection line ii.The pilot valve 48 may comprise a valve 50, a valve casing 5|. a valve'stem 52 entending through the ends of the casing 5|, aspring-restraining plate 53 attached to one end of the valve stem 52. aspring 54 compressed between the end of the casing 5i and the plate 53,an armature 56 attached to the other end of the valve stem 52, and

a solenoid 51 surrounding the armature 58. The

solenoid 51 and armature 56 may be encased in a protective housing 59.,if desired. The valve casing Si is provided with a centrally spaced port64 and two oflset ports 62 and 53. Attached to offset port 62 is a ventpipe 54 and to port 93 is a 80 and leads to the diaphragm chamber I0 ofthe diaphragm-motor valve 49. When current is applied to the solenoid51, the armature and the valve stem 52 and valve 50 attached theretoaremoved against the action of spring 54 to a position with the valve 59between the vent port 62 and the diaphragm port 60, whereby fluidcommunication between the gas supply port 53 and diaphragm port 50 isprovided. When the solenoid 51 is not energized, the valve is moved tothe other side of the diaphragm port 60 by the action of the spring 54whereby the pressure in the diaphragm chamber 10 is released throughport 62 and vent line 64.

The diaphragm-motor valve 49 may be of any suitable type adapted to openwhen pressure is applied to one side of its diaphragm and may, in

a preferred form, comprise diaphragm chamber diaphragm H and tending toclose the valve 12.

'In the electrical circuit, such as in conductor 42, from the centralregulator 2i to the control valve 24 is a normally closed circuitinterrupter 21 adapted to break the electrical circuit in response to acertain condition (pressure, impact, rate of flow, etc.) in thedischarge line l0 due to flow of liquid or oil therethrough. Forexample, a suitable arrangement comprises 9. diaphragm exposed to thepressure in the flow line l0 near the well head, a stem 8i attached atone end to the diaphragm 80, a normally closed switch operativelyconnected to the other end of the stem 8|, and a spring 83 actingagainst the low pressure side of the diaphragm 80 and tending to closethe switch. The switch is preferably adapted, for example, by means of atoggle arrangement, to open at a predetermined high pressure and toreturn .to closed position at a predetermined lower pressure. In apreferred form, as shown in Figure IV, the switch may comprise a pair ofstationary contacts terminating the break in the electrical conductor42, a movable contact 9i adapted to bridge said pair of stationarycontacts 90 and carried at one end of an arm 92 pivoted at the other endon a shaft 91 carried by the housing 95, and a toggle spring 93 linkingthe center of the arm 92 to the stem 8i. The contacts 90 are supportedon a bracket 94 extending from the inner wall of the switch housing 95.The swing of the pivoted arm 92 is limited in one direction by thecontacts 90 and bracket 94 and in the other direction by a stop 95. Bysuitably adjusting or selecting the springs 83 .and 93, the opening andclosing pressures of the switch can be controlled.

, the discharge line In.

tion of the contact 36 pressing against the spaced contacts 4| of thering 40 causes the completion of the electrical circuits to the variouscontrol valves 24 in a predetermined sequence, whereby only one well ata time draws on the supply of pressure gas and violent fluctuations inthe pressure of the gas supply are avoided. On completing the electricalcircuit from the electrical current source 22 through stationary contact43, rotating ring 35 and contact 36, one of the individual contacts 4|in the ring 40, electrical conductor 42 and the closed interrupterswitch 90-93 to the solenoid 51, the armature 56 with the valve stem 52and valve 50 attached thereto are caused to be moved intodiaphragm-actuating position by the energization of the solenoid 51.With the valve 50 in this position, pressure gas passes from the gassupply line l6 through the small pipe 55, the valve casing 5|, thediaphragm port 60 and the conduit 61 into the diaphragm chamber 1|],wherein the pressure acts upon and depresses the diaphragm H and therebycauses the valve 12 attached to the diaphragm 1| by means of stem I3 tobe opened against the action of the spring 14.

Pressure gas then flows through the thusopened valve 12 down the annularspace 9 to the displacement chamber 5 and forces the accumulated liquidup the education tube 1 and out The flow of oil through the dischargeline causes an increase in the pressure on the diaphragm 80 of thecircuit interrupter 21. The pressure-responsive upward movement of thediaphragm 80 movesthe switch arm 92 attached thereto by stem 8| intoopen position at a predetermined pressure against the action of thespring 83, whereby the electrical circuit through line 42 from thecentral regulator 2| to the solenoid 51 of the control valve 24 isbroken. The armature 55 is then no longer pulled upward by the magneticfield of the solenoid and the valve 50 is moved to the opposite side ofthe diaphragm port 60 by the action of the spring 54, whereby the ports62 and 60 are in communication and the pressure in the diaphragm chamberi is vented to the atmosphere through vent conduit 64. With the releaseof pressure in the chamber ill, the diaphragm II is moved upward and thevalve 12 is closed by the action of spring 14. lift pump is shut off atthe optimum time, that is, when the oil flows from the dischargeor flowline H].

The gas then remaining in the annular space 9 expands, thereby furtherlifting the liquid in the eduction tube 1, and finally escapes throughthe discharge line Ill. During the expansion of the remaining pressuregas in the annular space 9 and its exhaustion from the gas-lift pump,the continued rotation of the ring 35 causes the electrical circuit tothe the control valve 24 of the well concerned to be broken-..Thereafter, the pressure against the diaphragm 80 of the circuitinterrupter 21 drops to a predetermined low pressure, at which thespring 8.3 re-closes the switch after overcoming the pressure in theline H! and, with the preferred form, also the. delayed action of thetoggle-type switch 9|l93. It is preferable that the diiference betweenopening and closing pressures of the circuit interrupter 21 should besubstantial in order to avoid accidental closing of the circuit due topressure pulsations. Then this well again passes through the stage ofaccumulation of well liquids in the chamber while a similar series ofactions are automatically ef- Thus, the supply of pressure gas to thegasfected in series on the other wells connected to the centralregulator 2| By means of the present gas-lift control system the mosteconomical gas consumption is obtained. The present control systemlikewise eliminates the necessity of frequent attendance of an oper--ator to adjust the length of the contacts 4| in the central regulator2|. Rather, the gas supply is automatically shut 0113 at the optimumtime, either by the central regulator 2| .or, if the lifting operationis effected in a time shorter than that for which the central regulatorhad been adjusted, by the circuit interrupter 21 in response to a flowof oil out through the discharge line l0. In other words, the workingperiod is roughly adjusted in the central regulator 2| by the length ofthe contact 4| and the fine adjustment to the optimum is obtained by theaction of the circuit interrupter 2|. In addition to efiecting adecrease in gas consumption, the present control system increases crudeoil production by increasing the liquid accumulation time and therebyincreasing the volume of oil raised in each operation of the gas-liftpump.

I claim as my invention:

1. In an intermittent gas-lift system comprising a plurality of Wells, asource of supply of pressure gas, and for each well a displacementchamber for liquid to be lifted, pressure conduit means communicatingwith said pressure gas source for admitting said gas to said chamber, anelectrically operated valve in said pressure con.- duit means forcontrolling the flow of said gas, and conduit means from said chamberfor discharging from said well the liquid raised by said gas, a controlsystem comprising a source of electric current, a circuit for each wellconnecting said electric source to the electrically operated valve forsaid well, a time-responsive intermitter common to said circuits forcyclically making and breaking said circuits in a predetermined.

sequence, and a normally closed interrupter at each well operated by theliquid discharged therefrom for breaking the circuit for each well.

2. In an intermittent gas-lift system comprising a plurality of wells, asupply of pressure gas,

valve-controlled conduit means for each well for admitting said gas tosaid wells, and conduit means for discharging from each well the liquidraised by said gas, a control system comprising an intermitter forcontrolling the cyclical opening and closing of the valves admitting thegas to the several wells, and an interrupter at each well operated bythe liquid discharged therefrom for controlling the closing of the valveadmitting the pressure gas to said well.

3. In an intermittent gas-lift system comprising a plurality of wells, asupply of pressure gas, valve-controlled conduit means for each well foradmitting said gas to said wells, and conduit means for discharging fromeach well the liquid raised by said gas, a control system comprising atime-responsive intermitter for controlling the cyclical opening andclosing of the valves admitting the gas to the several wells in apredetermined sequence, and an interrupter at each well operated by theliquid discharged therefrom for controlling the closing of thevalveadmitting the pressure gas to said well.

4. In an intermittent gas-lift system comprising a plurality of wells, asupply of pressure gas, conduit means between said pressure gas supplyand each of said wells for admitting said gas thereinto, an electricallyoperated valve in each of said pressure conduit means for controllingthe flow of said gas, and conduit means for discharging from each wellthe liquid raised by said gas, a control system comprising a sourceelectric current, a circuit for each well connecting said source to theelectrically operated valve for said well, an intermitter for cyclicallymaking and breaking said circuits, thereby controlling the cyclicalopening and closing of said valves, a normally closed interrupter ineach circuit adapted to break said circuit, thereby controlling theclosing of said valve independently of the intermitter, and meansactuated by the liquid discharged from the well controlled by saidcircuit for opening said interrupter.

5. In an intermittent gas-lift system comprising a plurality of wells, asupply of pressure gas, conduit means between said pressure gas supplyand each of said wells for admitting said gas thereinto, an electricallyoperated valve in each of said means for controlling the flow of saidgas, and conduit means for discharging from each well the liquid raisedby said gas, a control system comprising a source of electric current, acircuit for each well connecting said source to the electricallyoperated valve for said ,well, a time-responsive intermitter forcyclically making and breaking said circuits in a predeterminedsequence, thereby controlling the cyclical opening and closing of saidvalves, a normally closed interrupter in each circuit adapted to breaksaid circuit, thereby controlling the closing of said valveindependently of the intermit ter, and means actuated by the liquiddischarged from the well controlled by said circuit for opening saidinterrupter.

6. In an intermittent gas-lift system comprising a plurality of wells, asupply of pressure gas, conduit means between said pressure gas supplyand each of said wells for admitting said gas thereinto, an electricallyoperated valve in each of said means for controlling the flow of saidgas, and conduit means for discharging from each well the liquid raisedby said gas, a control system comprising a source of electric current, acircuit for each well connecting said source to the electricallyoperated valve for said well, a time-responsive intermitter forcyclically making and breaking said circuits in a predeterminedsequence, thereby controlling the cyclical opening and closing of saidvalves, a normally closed interrupter in each circuit adapted to breaksaid circuit, thereby controlling the closing of said valveindependently of the intermitter, and

7. In an intermittent gas-lift system comprising a plurality of wells, asupply of pressure gas, conduit means between said pressure gas supplyand each of said wells for admitting said gas thereinto, an electricallyoperated valve in each of said means for controlling the flow of saidgas, and conduit means for discharging from each well the liquid raisedby said gas, a control system comprising a source or electric current, acircuit for each well connecting said source to the electricallyoperated valve for said well, a time-responsive intermitter common tosaid circuits for cyclically making and breaking said circuits in apredetermined sequence, thereby controlling the cyclical opening andclosing of said valves, a normally closed interrupter in each circuitadapted to break said circuit, thereby controlling the closing of saidvalve independently of the intermitter, and means responsive to thepressure in the liquid discharge conduit of the .well controlled by saidcircuit for opening said interrupter, and resilient means adapted toovercome a predetermined lower pressure in said conduit for closing saidinterrupter.

8. In an intermittent gas-lift system comprising a plurality of wells, asource of supply of pressure gas, and for each well a displacementchamber for liquid to be lifted, pressure conduit means communicatingwith said pressure gas source for admitting said gas to said chamber,

an electrically operated valve in said pressureconduit means forcontrolling the flow of said gas, and conduit means from said chamberfor discharging from said well the liquid raised by said gas, a controlsystem comprising a source rupter in open position when liquid isdischarged from the well.

I-IENDRK PIETER DE WIT.

